U.S. patent application number 10/782816 was filed with the patent office on 2005-01-20 for circulating body and fixing device.
This patent application is currently assigned to Fuji Xerox Co., Ltd.. Invention is credited to Inamura, Kei, Komuro, Hitoshi, Nakatogawa, Kenji, Tamemasa, Hiroshi, Tsutsumi, Yousuke.
Application Number | 20050013639 10/782816 |
Document ID | / |
Family ID | 34056179 |
Filed Date | 2005-01-20 |
United States Patent
Application |
20050013639 |
Kind Code |
A1 |
Komuro, Hitoshi ; et
al. |
January 20, 2005 |
Circulating body and fixing device
Abstract
In a circulating body driven with its surface being circulated
along a fixed route and comprising a base material having a tubular
outside peripheral surface and a surface layer covering the outside
peripheral surface of the base material, the surface static
friction coefficient of the surface layer is designed to be 0.06 or
less with common paper at 100.degree. C.
Inventors: |
Komuro, Hitoshi;
(Minamiashigara, JP) ; Tamemasa, Hiroshi;
(Minamiashigara, JP) ; Tsutsumi, Yousuke;
(Minamiashigara, JP) ; Nakatogawa, Kenji;
(Minamiashigara, JP) ; Inamura, Kei;
(Minamiashigara, JP) |
Correspondence
Address: |
MORGAN LEWIS & BOCKIUS LLP
1111 PENNSYLVANIA AVENUE NW
WASHINGTON
DC
20004
US
|
Assignee: |
Fuji Xerox Co., Ltd.
|
Family ID: |
34056179 |
Appl. No.: |
10/782816 |
Filed: |
February 23, 2004 |
Current U.S.
Class: |
399/328 |
Current CPC
Class: |
G03G 2215/2009 20130101;
G03G 15/2057 20130101 |
Class at
Publication: |
399/328 |
International
Class: |
G03G 015/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2003 |
JP |
2003-277000 |
Claims
What is claimed is:
1. A circulating body driven with its surface being circulated
along a fixed route, the circulating body comprising: a base
material having a tubular outside peripheral surface; and a surface
layer covering the outside peripheral surface of the base material
and having a surface static friction coefficient of 0.06 or less
with common paper at 100.degree. C.
2. A circulating body according to claim 1, wherein the surface
layer comprising a fluororesin containing an inorganic fine
particle.
3. A circulating body according to claim 2, wherein the surface
layer containing the inorganic fine particle in an amount of 1 mass
% or more and 30 mass % or less based on 100 mass parts of the
fluororesin.
4. A circulating body according to claim 2, wherein the surface
layer contains, as the inorganic fine particle, at least one fine
particle selected from the group consisting of a metal oxide fine
particle, a mineral silicate fine particle and a metal nitride fine
particle.
5. A circulating body according to claim 2, wherein the surface
layer contains, as the inorganic fine particle, at least one fine
particle selected from the group consisting of a BaSO.sub.4 fine
particle, a tin oxide fine particle, a zeolite fine particle, a
mica fine particle and a boron nitride fine particle.
6. A circulating body according to claim 2, wherein the surface
layer containing an inorganic fine particle having an average
particle diameter of 0.1 .mu.m or more and 15 .mu.m or less.
7. A circulating body according to claim 2, wherein the surface
layer containing an inorganic fine particle which has an average
particle diameter of 0.1 .mu.m or more and 15 .mu.m or less and
contains a particle having a particle diameter of 15 .mu.m or more
in an amount of 25 mass % or less.
8. A circulating body according to claim 2, wherein the surface
layer containing a conductive fine particle in an amount of 1 mass
part or more and 10 mass parts or less based on 100 mass parts of
the fluororesin.
9. A circulating body according to claim 2, wherein the surface
layer containing a copolymer of tetrafluoroethylene and
perfluoroalkyl vinyl ether as the fluororesin.
10. A circulating body according to claim 9, wherein the surface
layer containing, as the fluororesin, a composition of plural type
of particles differing in the particle diameter of the copolymers
wherein a second particle having an average particle diameter of 3
.mu.m or more and 30 .mu.m or less is compounded in an amount of 5
mass parts or more and 70 mass parts or less based on 100 mass
parts of a first particle having an average particle diameter of 1
.mu.m or less.
11. A circulating body according to claim 10, wherein the surface
layer uses, as the first particle, a particle having a melt
viscosity of 3.5.times.10.sup.4 Pa.multidot.s or less at
380.degree. C. and as the second particle, a particle having a melt
viscosity of 1.5.times.10.sup.4 Pa.multidot.s or less at
380.degree. C.
12. A circulating body according to claim 10, wherein the surface
layer uses, as both the first particle and the second particle, a
particle having a melt viscosity of 1.5.times.10.sup.4
Pa.multidot.s or less at 380.degree. C.
13. A circulating body according to claim 1, wherein the surface
layer has a surface roughness Ra of 3 .mu.m or less;
14. A circulating body according to claim 1, wherein the surface
layer has a surface gross of 15 or more and 60 or less as the value
measured by a 75.degree. micro-gloss meter (BYK Gardner).
15. A circulating body according to claim 1, wherein the surface
layer has a filtered wave center line waviness of 0.9 .mu.m or less
in the condition of 0.25 mm cutoff.
16. A circulating body according to claim 1, wherein the base
material has a roll-like shape, or a seamless belt-like shape.
17. A fixing device comprising: a rotating roll-like fixing member;
a fixing tubular body rotating along with the rotation of the
fixing member in contact with the fixing member; a press member
that is disposed inside of the fixing tubular body and presses this
fixing tubular body against the fixing member to form a nip zone
between the fixing tubular body and the fixing member; and a
heating source that heats the nip zone; to fix an unfixed toner
image to a recording medium by holding the recording medium
carrying the unfixed toner image in the nip zone, wherein the
fixing tubular body is provided with a seamless belt-like base
material and a surface layer covering the outside peripheral
surface of the base material and having a surface static friction
coefficient of 0.06 or less with common paper at 100.degree. C.
18. A fixing device according to claim 17, wherein the time
required for a point on the recording medium to pass through the
nip zone is 0.020 seconds or more.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a circulating body that is
used for a fixing device fixing an unfixed image under heating and
pressure in an image forming device such as copiers, printers and
facsimile machines and is driven in such a manner that its surface
is circulated along a fixed route and also to a fixing device using
the circulating body.
[0003] 2. Background Art
[0004] It is usually necessary to form a permanent image by fixing
an unfixed toner image formed on a recording sheet in copiers and
the like making use of an electrophotographic process. As the
fixing method, a solvent fixing method, pressure fixing method and
heat fixing method are known. Among these fixing methods, the
solvent fixing method has the drawback that solvent vapor is
emitted during fixing, giving rise to many problems concerning
odors and sanitation. The pressure fixing method has the drawback
that it is inferior in fixing characteristics to other fixing
methods. Accordingly, the solvent fixing method and the pressure
fixing method are both limited in the range of practical fields and
therefore, the heat fixing method in which a toner is melted under
heating to fuse it on a recording sheet (image-receiving material)
is widely used.
[0005] As a device used in such a heat fixing method, a heat fixing
device is known which has a heat roll (also called a fixing roll)
provided with a heater lamp inside of a cylindrical core bar and a
heat resistant releasable layer formed on the outside peripheral
surface of the core bar and a pressure roll disposed in pressure
contact with the heat roll and having a structure in which a heat
resistant elastic body layer is formed on the outside peripheral
surface of a cylindrical core bar. In the heat fixing device having
this structure, a pressure of 1 to 15 kg/cm.sup.2 (preferably 3 to
10 kg/cm.sup.2) is applied to the heat roll and the pressure roll
from each other and a recording sheet such as a common paper on
which an unfixed toner image is formed is inserted and passed
through between both rolls to thereby fix, and fixing using a heat
fixing roll system is thus carried out. In the heat fixing device
as aforementioned, the surface of the pressure roll is moved
circularly on a fixed route and this pressure roll is a sort of the
aforementioned circulating body.
[0006] The heat fixing device (heat roll type fixing device)
adopting this heat fixing roll system has higher heat efficiency
than devices using other fixing systems such as a hot air fixing
system and an oven fixing system and therefore, the heat fixing
device requires low power, is superior in high speed performance
and is reduced in danger of a fire caused by paper jamming. This
heat fixing device is therefore most widely used.
[0007] However, more energy saving and more promotion of fixing
speed are both desirably accomplished in recent heat fixing
devices. In order to satisfy this, it is necessary to increase the
width of a nip zone, namely a nip width, that actually sandwiches a
recording sheet when fixing under heating. Under this situation, a
belt nip type fixing device has been recently developed to solve
these problems.
[0008] As the belt nip type fixing device, for instance, a device
is known which is provided with a rotating heat fixing roll with a
built-in heating source, a resin film tubular body that is in
pressure contact with the heat fixing roll and is moved with
rotating together with the heat fixing roll and a pressure pad that
is disposed inside of the resin film tubular body and presses the
resin film tubular body against the heat fixing roll to form a nip
section between the resin film tubular body and the heat fixing
roll and fixes an unfixed toner image to a recording sheet by
passing the recording sheet through the nip section (see, for
example, Japanese Patent Application Laid-open No. 11-24457). In
such a belt nip type fixing device, the surface of the resin film
tubular body is moved circularly on a fixed route and is therefore
also a sort of the aforementioned circulating body.
[0009] As the circulating bodies such as the resin film tubular
body and the pressure roll, those having a layer of a copolymer
(hereinafter abbreviated as PFA if necessary) of
tetrafluoroethylene and perfluoroalkyl vinyl ether on the surface
and those having a rubber type surface are used to obtain
releasability from a recording sheet and a toner image.
[0010] Also, in the belt nip type fixing device, a lubricating
material such as a lubricant or a low-friction film is interposed
between the pressure pad and the resin film tubular body to thereby
reduce sliding resistance between the resin film tubular body and
the fixed pressure pad.
[0011] However, the belt nip type fixing device has the problem
that when the lubricating material is thermally deteriorated or
worn with working time, the sliding resistance between the resin
film tubular body and the fixed pressure pad is raised, with the
result that the running of the recording sheet becomes unstable,
leading to occurrences of paper wrinkles and image defects.
[0012] Such a problem is a particular one regarded as important in
the belt nip type fixing device. However, this problem is not
exclusive in the belt nip type fixing device but possibly arises
likewise even in the aforementioned heat roll type fixing device in
the case where the resistance of the pressure roll (circulating
body) is increased when its surface is circulated.
SUMMARY OF THE INVENTION
[0013] The present invention has been made in view of the above
circumstances and provides a solution to the above problem and a
highly reliable circulating body that can prevent the unstable
running of a recording sheet, paper wrinkles and image defects and
also a highly reliable fixing device using the circulating
body.
[0014] According to the present invention, there is provided a
circulating body driven with its surface being circulated along a
fixed route, the circulating body comprising:
[0015] a base material having a tubular outside peripheral surface;
and
[0016] a surface layer covering the outside peripheral surface of
the base material and having a surface static friction coefficient
of 0.06 or less with common paper at 100.degree. C.
[0017] The inventors of the present invention have made earnest
studies and as a result, found that the running stability of a
recording sheet in the case where the resistance of a circulating
body when its surface is circulated is raised along with a change
with time is improved when the friction coefficient of the surface
layer is dropped to the above value or less and the occurrences of
paper wrinkles and image defects are remarkably suppressed. This
reason is considered to be that when a recording sheet is passed
through the aforementioned nip zone, a rise of the sliding
resistance of the circulating body has such an influence as to
brake the transfer of the recording sheet in usual whereas, in the
present invention, a phenomenon occurs that the above influence is
lessened because the surface of the circulating body and the
surface of the sheet are slipped on each other. This phenomenon
emerges when the friction coefficient is dropped to the above value
or less.
[0018] According to the present invention, there is provided a
fixing device comprising:
[0019] a rotating roll-like fixing member;
[0020] a fixing tubular body rotating along with the rotation of
the fixing member in contact with the fixing member;
[0021] a press member that is disposed inside of the fixing tubular
body and presses the fixing tubular body against the fixing member
to form a nip zone between the fixing tubular body and the fixing
member; and
[0022] a heating source that heats the nip zone; to fix an unfixed
toner image to a recording medium by holding a recording medium
carrying an unfixed toner image in the nip zone, wherein;
[0023] the fixing tubular body is provided with a seamless
belt-like base material and a surface layer covering the outside
peripheral surface of the base material and having a surface static
friction coefficient of 0.06 or less with common paper at
100.degree. C.
[0024] According to the fixing device of the present invention, a
recording sheet can be slipped through the nip zone by the surface
layer having a surface static friction coefficient of 0.06 or less
even if the resistance of the fixing tubular body during rotation
is increased with the result that the running stability of a
recording sheet is high and the occurrence of paper wrinkles and
image defects can be remarkably suppressed.
[0025] According to the present invention, a circulating body that
is highly reliable for a long time and can be significantly limited
in the unstable running condition of a paper and the occurrence of
paper wrinkles and image defects even if the resistance when the
surface is circulated is increased and a highly reliable fixing
device can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Preferred embodiments of the present invention will be
described in detail based on the following figures, wherein:
[0027] FIG. 1 is a sectional view typically showing a first
embodiment of the present invention; and
[0028] FIG. 2 is a sectional view typically showing a second
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The embodiments of the present invention will be described
with reference to the drawings.
[0030] FIG. 1 is a sectional view typically showing a first
embodiment of the present invention.
[0031] FIG. 1 shows a heat fixing device 100 and a recording sheet
S provided with an unfixed toner image formed on its surface.
[0032] The heat fixing device 100 shown in FIG. 1 is a device
aiming at both the promotions of small size-energy saving and
high-speed. The heat fixing device 100 is provided with a heating
roll 110 that melts an unfixed toner S1 put on the recording sheet
S under heating and a pressure section 120 that presses the molten
unfixed toner S1 against to the recording sheet S.
[0033] The heating roll 110 is provided with a heat source 112
inside of an aluminum core body 111 having a cylindrical form, a
heat resistant elastic body layer 113 made of a silicone rubber is
disposed around the core body 111 and a heat resistant peelable
layer 114 made of a fluororesin is further disposed around the heat
resistant elastic body layer 113. The structure of the heating roll
110 is a usual one which has been known so far and not only the
structure shown here but also other known structures may be
adopted. The following explanations will be furnished on the
premise that the structure shown in FIG. 1 is adopted.
[0034] A temperature sensor 115 is also provided that controls the
temperature of the surface of the heating roll 110 at a fixed
position in contact with the surface of the heating roll 110. The
heat source 112 is turned on or off according to the temperature
detected by the temperature sensor 115 and the surface temperature
of the heating roll 110 is controlled to the temperature necessary
to fix the toner S1 to the recording sheet S.
[0035] In the meantime, the pressure section 120 is provided with a
pressure belt 121, a pressure pad 122 that presses the pressure
belt 121 against the heating roll 110 from the inside, a support
member 123 that supports this pressure pad 122 and a belt running
guide 124 that aids the running of the pressure belt 121.
[0036] The fixing device provided with the heating roll 110 and the
pressure belt 121 in this manner is called a heat roll-belt type
fixing device.
[0037] The pressure belt 121 of the pressure section 120 is in
pressure contact with the heating roll 110 by the pressure pad 122.
Therefore, when the heating roll 110 is rotated in the direction of
the arrow A in the figure by a motor (not shown), the pressure belt
121 follows the heating roll 110 and is rotated and moved in the
direction of the arrow B. In the pressure section 120, a support
roll and a pressure roller for holding and spreading the pressure
belt 121 are not present and the pressure belt 121 is guided along
a belt running guide 124 and driven by driving force from the
heating roll 110. Fixing devices like this are called a free-belt
fixing device to discriminate it from a type having a support roll
and a pressure roll.
[0038] The pressure pad 122 is pressed against the pressure belt
121 through a low-friction material (illustration is omitted) such
as a glass fiber sheet including Teflon (trademark) or fluororesin
sheet and a nip zone R where the pressure belt 121 has a shape
concaved in the pressure section 120 side is formed.
[0039] The recording sheet S transferred from the upstream side of
the transfer route (not shown) is passed through the nip zone R
between the heating roll 110 and the pressure belt 121 and
transferred to the downstream side. When the recording sheet S is
passed through the nip zone R, the unfixed toner S1 on the
recording sheet S is heated and melted by the heat source 112.
Also, at this time, the recording sheet S is pressed against the
heating roll 110 by the pressure pad 122 with the pressure belt 121
being interposed between the recording sheet S and the pressure pad
122, whereby the toner image is fixed to the recording sheet S. The
recording sheet S after fixed is peeled from the heating roll 110
by a peeling click (not-shown) after passed through the nip zone R
and then discharged from the heat fixing device 100.
[0040] The pressure pad 122 disposed inside of the pressure section
120 is preferably made of two parts that are disposed side by side
and differ in hardness. If, for example, the part on the side
(upstream side) where the recording sheet is inserted is
constituted of a rubber-like elastic member and the part on the
side (downstream side) where the recording sheet is discharged is
constituted of a hard pressure-imparting member such as metals, the
pressure to be applied to the recording sheet in the nip zone is
higher in the downstream side than in the upstream side, with the
result that the releasability of particularly, a thin recording
sheet is improved.
[0041] Also, the time (nip time) required for the recording sheet S
to pass through the nip zone R is desirably 0.020 seconds or more.
When the nip time is shorter than 0.020 seconds, it is difficult to
attain both the good fixing characteristics and the prevention of
paper wrinkles and curling and it is therefore necessary to raise
fixing temperature corresponding to a reduction in the nip time,
which brings about waste of energy, a reduction in the durability
of parts and a rise in the temperature of the device, which is
undesirable. Although no particular limitation is imposed on the
upper limit of the nip time, the upper limit of the nip time is
preferably 0.5 seconds or less from the viewpoint of the balance
between fixing capacity and the sizes of the device and
members.
[0042] The parts having the characteristics of the embodiment of
the present invention are the pressure section 120 and the pressure
belt 121 and the details of the pressure belt 121 will be
hereinafter explained.
[0043] The pressure belt 121 is an endless belt constituted of a
seamless belt-like base material 125 and a surface layer 126
covering the outside peripheral surface of the base material 125
and the surface layer 126 has a surface static friction coefficient
of 0.06 or less with common paper at 100.degree. C.
[0044] As the base material 125, any material may be used as far as
this pressure belt 121 (endless belt) has a strength enough to
rotate following the heating roll 110 and, for example, a polymer
film, metal film, ceramics film, glass fiber film or complex film
obtained by compounding two or more of these films may be used.
Examples of the polymer film include sheet-like or cloth-like
products such as polyesters such as a polyethylene terephthalate,
polycarbonates, polyimides, fluorine type polymers such as a
polyvinyl fluoride and tetrafluoroethylene, polyamides such as
nylon, polystyrenes and polyacryls, polyethylenes and
polypropylenes, cellulose modified materials such as polycellulose
acetates, polysulfones, polyxylylenes and polyacetals. Further,
examples of the polymer film may also include polymer complex
products obtained by laminating, for example, a fluorine type,
silicone type or crosslinking polymer type heat resistant resin
layer. The base material is particularly preferably constituted of
an endless belt like heat resistant resin (e.g., a polyimide resin)
among these materials.
[0045] Also, such a polymer film may be combined with a heat
resistant layer formed of a metal or ceramics. Also, a heat
conductivity improver such as granular, needle or fiber-like carbon
black, graphite, alumina, silicon, carbide and boron nitride may be
added in the inside of the polymer film. Also, additives such as an
electroconductive improver, antistatic agent, release agent and
reinforcing agent may be added or applied to the inside or the
surface of the polymer film according to the need. Besides the
above polymer films, papers such as condenser paper and glassine
paper, ceramics type films or glass fiber films formed cloth-wise
using glass fiber and metal films such as stainless films and
nickel films may be used.
[0046] The thickness of the base material 125 is preferably 30
.mu.m to 250 .mu.m and more preferably 50 .mu.m to 150 .mu.m.
[0047] In this embodiment, an adhesive called a primer is applied
and then a surface layer 126 constituted of a copolymer (PFA) of
tetrafluoroethylene and a perfluoroalkyl vinyl ether in which a
filler particle is compounded as will be described later for
pretreatment forming the surface layer. However, an embodiment in
which the surface layer 126 is directly formed on the endless
belt-like non-sintered base material or an embodiment in which an
intermediate layer such as a heat resistant elastic layer is
disposed between the base material 125 and the surface layer 126 as
required are preferable embodiments.
[0048] As the structural material of the surface layer 126, a PFA
which is superior in heat resistance and flexibility particularly
necessary for structural parts of the heat fixing device from among
fluororesins having low adhesiveness and high releasability is
adopted as a major material. The friction coefficient of the
surface with paper at high temperatures is dropped to the above
value or less by compounding a specific filler material in this PFA
as will be explained later. As a consequence, such a high
reliability is attained that even if sliding resistance along with
the rotation and movement of the pressure belt 121 is increased,
the running stability of paper is high and the occurrences of paper
wrinkles and image defects can be prevented for a long term while
maintaining high releasability from a toner and high
durability.
[0049] If only a PFA is used as usual as the structural material of
the surface layer, the friction coefficient with a paper at high
temperatures is high because of the smoothness of the PFA, giving
rise to the problem that paper wrinkles are caused in the case
where the sliding resistance of a circulating body (pressure belt)
is raised when using a device with time. On the contrary, when a
specific filler particle is compounded in the PFA as aforementioned
in this embodiment, the friction coefficient of the surface with a
paper is dropped. Therefore, the running stability of a paper is
kept high when sliding resistance is increased and it is also
possible to improve abrasion resistance.
[0050] The filler particle to be compounded in the surface layer
126 (PFA film) is an inorganic fine particle and preferably
contains at least one fine particle selected from the group
consisting of metal oxide fine particles, mineral silicate fine
particles and metal nitride fine particles. Also, this filler
particle more preferably contains at least one fine particle
selected from the group consisting of BaSO.sub.4 fine particles,
tin oxide fine particles, zeolite fine particles, mica fine
particles, and boron nitride fine particles and is particularly
preferably a BaSO.sub.4 fine particle.
[0051] As the metal oxide fine particle used for the filler
particle, fine particles of silicon oxide, copper oxide, iron oxide
and zirconium oxide besides tin oxide fine particles may be
adopted. Also, as the metal nitride fine particle used for the
filler particle, fine particles of silicon nitride and titanium
nitride besides boron nitride fine particles may be adopted.
[0052] Various surface characteristics of the surface layer 126 can
be controlled by compounding the aforementioned filler particle in
the fluororesin (particularly PFA) and by selecting the type of
material and the amount of to be compounded. Desirable
characteristics will be mentioned hereinbelow.
[0053] The center average surface roughness (Ra) of the surface
layer 126 is preferably in a range of 3 .mu.m or less. When the
surface roughness is larger than 3 .mu.m, the surface gloss of the
surface layer is dropped, giving rise to the problem that the gloss
of a fixed image when forming an image on both surfaces is dropped.
Also, the problem probably arises that when some roughness appears,
the roughness affects an image.
[0054] Also, the surface layer 126 has a surface gloss ranging
preferably from 15 to 60 and more preferably 20 to 50 as a value
measured by a 75.degree. micro-gloss meter. When the surface gloss
is smaller than 15, the gloss of the fixed image tends to be
dropped when forming an image on both surfaces. Also, in the case
of glossy coated paper, the gloss of an image is lower than that of
a paper and there is therefore the case where the quality of the
output product is deteriorated. On the other hand, when the surface
gloss exceeds 60, there is the case where the adhesion of the
surface layer to a paper is too high, causing paper wrinkles.
[0055] Moreover, the surface layer 126 has a filtered wave center
line waviness of preferably 0.9 .mu.m or less and more preferably
0.7 .mu.m or less in the condition of 0.25 mm cutoff. When a wave
pattern (slow irregularities, height: several .mu.m, pitch: 0.05 to
several mm) appears on the surface of the surface layer 126, this
leads to transmission unevenness of OHPs. It is possible to prevent
transmission unevenness of OHPs by making the filtered wave center
line waviness fall in the above range.
[0056] Although the proportion of the filler particle to be
compounded in the surface layer (PFA film) may be set to a desired
proportion, the proportion of the filler particle to be compounded
is preferably in a range from 1 mass part to 30 mass parts and more
preferably in a range from 3 mass parts to 15 mass parts based on
100 mass parts of the fluororesin.
[0057] When the proportion of the filler particle to be compounded
is less than 1 mass part, scratches and the like are easily
generated on the surface of a pressure belt and the friction
coefficient of the surface with a paper at high temperatures is
raised because abrasion resistance to contact materials such as a
peeling click is inferior though the surface layer has high
releasability from a toner and a paper due to high releasability
that the PFA has. For this, the aforementioned advantages in this
embodiment, namely, the advantages that even if sliding resistance
of the pressure belt is increased, the running stability of a paper
is high and the occurrences of paper wrinkles and image defects can
be prevented for a long term while maintaining high releasability
from a toner and high durability are damaged.
[0058] Also, if the proportion of the filler particle to be
compounded exceeds 30 mass parts, it is difficult to obtain a
uniform dispersion state of the filler particle, causing not only
uneven film thickness but also a reduction in the high
releasability that the PFA has and toner offset tends to be caused.
Also there is the case where the surface characteristics of the
surface layer such as surface roughness and gloss are deviated from
the above range and the gloss of an image is dropped and a rough
image appears.
[0059] The average particle diameter of the filler particle is
preferably 0.1 .mu.m or more and 15 .mu.m or less, more preferably
1 .mu.m or more and 10 .mu.m or less and still more preferably 2
.mu.m or more and 8 .mu.m or less. The filler particle has a
particle having a size of 15 .mu.m or more in an amount of
preferably 25 mass % or less, more preferably 5 mass % or less and
still more preferably 3 mass % or less from the viewpoint of
avoiding the generation of fine acute projections on the surface
layer and obtaining a surface having fine cavities.
[0060] When the average particle diameter of the filler particle is
less than 0.1 .mu.m, the gross surface area of powders becomes
excessively large and there is the case where it is difficult to
disperse the filler particle uniformly when it is added to the PFA.
Also, when the average particle diameter of the filler particle is
larger than 10 .mu.m, there is the case where the problem that the
surface of the surface layer is too roughened arises. Also, when
the amount of particles having a particle diameter larger than 15
.mu.m or more exceeds 5 mass %, the filler particles having a large
particle diameter tend to form acute projections like prickles.
These acute projections pierces an image when an image is formed on
both surfaces and there is the case where white void-like image
defects are caused. The filler particle may contain particles 15
.mu.m or less in size in an amount up to 25 mass % or less in the
case of forming the surface layer 126 through a step of cutting the
acute projections.
[0061] As the filler particle, a conductive particle may be used.
For example, there is the case where it is demanded of the pressure
belt 121 to have conductivity to prevent image deterioration
resulting from disturbance of an unfixed toner caused by the
electrification of the pressure belt 121. In this case, a
conductive particle is compounded as the filler particle to form
the surface layer 126 to thereby be able to impart conductivity to
the pressure belt 121. As the conductive particle, carbon black,
ITO (tin doped indium oxide) or the like may be used. When a
conductive particle is used as the filler particle, the conductive
particle is preferably compounded in a proportion of 1 mass part or
more and 10 mass parts or less based on 100 mass parts of the PFA
in consideration of such an object as to impart conductivity, the
viewpoint of maintaining the releasability of the PFA and such an
object as to obtain the good dispersibility of the conductive
particle.
[0062] The surface characteristics of the surface layer 126 can be
improved by compounding the filler particle as aforementioned.
Further, if the surface layer 126 is made using a composition of
plural types of PFA particles differing in particle diameter and by
properly selecting particle diameter, compounding ratio and melt
viscosity, the surface characteristics can be more improved.
[0063] The thickness of the surface layer 126 is preferably 5 .mu.m
to 100 .mu.m and more preferably 15 .mu.m to 60 .mu.m. In order to
obtain the surface layer 126 having a such preferable layer
thickness and high durability, it is preferable to use a
composition of two types of PFA particles differing in particle
diameter. Only a PFA particle that has a low melt viscosity, is
easily meltable and has a small particle diameter may be used
taking it only into consideration to form a non-wavy and smooth
surface layer 126. In the case of forming the surface layer 126
having a thickness of 20 .mu.m or more in one filming step using
only a PFA particle having a small particle diameter, there is the
problem that cracks occur on the surface. On the other hand, the
thickness of the surface layer 126 is excessively small, the
surface layer is worn by long term use, impairing the durability.
On the contrary, if two types of PFA particles are used, the film
thickness of the surface layer 126 that can be formed without any
crack in one filming step can be extended to the order of about 60
.mu.m and a highly durable surface layer can be materialized at a
low cost.
[0064] Among these two types of PFA particles, a PFA particle
having a small particle diameter (hereinafter referred to as a PFA
fine particle) preferably has an average particle diameter of 1
.mu.m or less and a PFA particle having a large particle diameter
(hereinafter referred to as a PFA powder) preferably has an average
particle diameter of 3 .mu.m or more and 30 .mu.m or less. The
average particle diameter of the PFA powder is more preferably 3
.mu.m or more and 15 .mu.m or less and still more preferably 6
.mu.m or more and 10 .mu.m or less. Also, as to the ratio of two
types of PFA particles in the composition used for the production
of the surface layer 126, a PFA powder having an average particle
diameter of 3 .mu.m or more and 30 .mu.m or less is contained in an
amount of preferably 5 mass parts or more and 70 mass parts or
less, more preferably 5 mass parts or more and 30 mass parts or
less and still more preferably 10 mass parts or more and 20 mass
parts or less per 100 mass parts of a PFA fine particle constituted
of a small diameter particle having an average particle diameter of
1 .mu.m or less. From the viewpoint of more improving the waviness
of the surface layer, the formulation of the above composition is
as follows: a PFA powder having an average particle diameter of 3
.mu.m or more and 15 .mu.m or less is contained in an amount of
preferably 5 mass parts or more and 30 mass parts or less and more
preferably 10 mass parts or more and 20 mass parts or less per 100
mass parts of a PFA fine particle.
[0065] Here, when the average particle diameter of the PFA powder
is smaller than 3 .mu.m and the amount of the PFA powder is less
than 5 mass parts per 100 mass parts of the PFA fine particle,
cracks tend to be caused on the surface layer 126. On the other
hand, when the average particle diameter of the PFA powder is
larger than 15 .mu.m and the amount of the PFA powder is larger
than 30 mass parts per 100 mass parts of the PFA fine particle, the
PFA powder is insufficiently melted during sintering and there is
the case where waviness (obtuse angle convex) due to a PFA particle
that has not been melted occurs on the surface of the surface layer
126.
[0066] These two types of PFA particles differing in particle
diameter preferably have the characteristics that the melt
viscosity of the PFA fine particle is 3.5.times.10.sup.4
Pa.multidot.s or less at 380.degree. C. and the melt viscosity of
the PFA powder is 1.5.times.10.sup.4 Pa.multidot.s or less at
380.degree. C. Both the PFA fine particle and the PFA powder have a
melt viscosity of preferably 1.5.times.10.sup.4 Pa.multidot.s or
less, more preferably 1.0.times.10.sup.4 Pa.multidot.s or less and
most preferably 0.5.times.10.sup.4 Pa.multidot.s or less at
380.degree. C. from the viewpoint of more improving the waviness of
the surface layer. If the melt viscosity of PFA at 380.degree. C.
exceeds 1.5.times.10.sup.4 Pa.multidot.s, the spread of the molten
PFA is low and there is the case where waviness occurs on the
surface of the surface layer 126.
[0067] It is simple to use a method in which a PFA coating solution
prepared by dispersing a PFA particle in a liquid medium is applied
to the base material 125 and sintered to manufacture the surface
layer 126 in this embodiment. At this time, as the liquid medium,
organic solvents such as water and alcohols or mixtures of water
and organic solvents may be used. Also, it is preferable to use a
surfactant to disperse the PFA particle in the liquid medium. As
the surfactant, anionic surfactants and nonionic surfactants are
preferable and nonionic surfactants are particularly preferable.
These surfactants may be used either singly or in combinations of
two or more. The surfactant is used in a ratio enough to disperse
the PFA particle uniformly in the liquid medium though no
particular limitation is imposed on the amount to be used. It is
preferable to use a thickener to make it easy to control film
thickness and to apply the PFA coating solution. Although no
particular limitation is imposed on the amount of the thickener to
be used, the amount is preferably adjusted corresponding to the
coating method to make it easy to apply. In the case of compounding
the aforementioned two types of PFA particles, procedures are
preferable in which a PFA powder is mixed in a dispersion solution
prepared by dispersing a PFA fine particle in a liquid medium mixed
with a surfactant, although no particular limitation is imposed on
the procedures for preparing the PFA coating solution. There is no
particular limitation is imposed on a method of applying a PFA
coating solution and a known method such as a dipping method, blade
coating method and spray method may be used.
[0068] As explained above, the surface characteristics (friction
coefficient, waviness, gloss and the presence or absence of fine
acute projections and fine cavities) of the surface layer 126 can
be improved by controlling the materials and proportions of the
fluororesin and filler particle constituting the surface layer 126,
whereby it is possible to suppress the occurrence of paper wrinkles
for a long period of time and to obtain a high quality image (image
improved in gloss unevenness when forming an image on both
surfaces, image transmission unevenness of OHP papers, white voids
of an image and paper end abrasion traces) while maintaining high
releasability from a toner and high durability.
[0069] As aforementioned, an embodiment in which the circulating
body of the present invention is applied to the pressure belt 121
is explained. However, the circulating body of the present
invention may also be applied to the form of a roll-like
member.
[0070] A second embodiment provided with a roll-like member to
which the circulating body of the present invention is applied will
be hereinafter described.
[0071] FIG. 2 is a sectional view typically showing the second
embodiment of the present invention.
[0072] In this FIG. 2, a heat fixing device 200 is shown. This heat
fixing device 200 is provided with the same heating roll 110 that
is shown in FIG. 1 and a pressure roll 220 in place of the pressure
section 120 shown in FIG. 1.
[0073] The pressure roll 220 shown here is constituted of a
roll-like base material 221 and a surface layer 222 covering the
outside periphery of the base material 221. The pressure section
220 is pressed by the heating roll 110, whereby a nip zone Q
concaved toward the heating roll 110 side is formed between the
pressure section 220 and the heating roll 110.
[0074] The surface layer 222 of the pressure roll 220 is
manufactured using the same material as the surface layer 126 of
the pressure belt 121 shown in FIG. 1 such that the same surface
characteristics are obtained. For this, similarly to the pressure
belt 121, this pressure roll 220 suppresses the occurrence of paper
wrinkles for a long period of time and serves to obtain a high
quality image while maintaining high releasability from a toner and
high durability.
[0075] As another embodiment of a heat fixing device to which the
circulating body of the present invention is applied, there is an
embodiment in which the pressure belt 121 shown in FIG. 1 is driven
by a motor and the heating roll 110 side is driven by the pressure
belt 121. In the heat fixing device having this structure, the
circulating body of the present invention is applied to the heating
roll side driven by the pressure belt 121.
[0076] In each of the aforementioned embodiments, one heat source
is disposed in the heating roll. However, the fixing device of the
present invention may be provided with plural heat sources and also
a heat source may be disposed outside the circulating body in the
present invention.
EXAMPLE
[0077] As examples of the present invention, seven examples will be
described in which the material and surface characteristics of the
surface layer of the pressure belt in a heat fixing device having
the same fundamental structure as the heat fixing device 100 shown
in FIG. 1 are changed within the values defined in the present
invention. As comparative examples to be compared with the
examples, three comparative examples will be explained in which the
surface characteristics of the surface layer of the pressure belt
in a heat fixing device having the same fundamental structure as
the heat fixing device 100 shown in FIG. 1 are deviated from the
values defined in the present invention. Also, the results of
evaluation in each of the examples and comparative examples will
also be explained.
[0078] Tables 1 and 2 shown below are tables which collectively
show the materials, characteristics and results of evaluation in
these examples and comparative examples. Explanations will be
furnished with reference to these Tables.
1TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5
Structure of a PFA PFA powder (Low melt (Low melt (Low melt (Low
melt (Low melt surface layer (100 mass parts) (average particle
viscosity) viscosity) viscosity) viscosity) viscosity) composition
diameter/mass parts) (8 .mu.m/15) (8 .mu.m/15) (8 .mu.m/15) (8
.mu.m/15) (8 .mu.m/15) Small particle diameter (Low melt (Low melt
(Low melt (Low melt (Low melt PFA (average particle viscosity)
viscosity) viscosity) viscosity) viscosity) diameter/mass parts)
(0.2 .mu.m/85) (0.2 .mu.m/85) (0.2 .mu.m/85) (0.2 .mu.m/85) (0.2
.mu.m/85) Filler BaSO.sub.4 (BMH-60) (BMH-60) (mass parts) (average
particle (5 .mu.m/10) (5 .mu.m/5) diameter/mass parts) Zeolite
(Toyobuilder) (average particle (2 .mu.m/5) diameter/mass parts)
Mica (Iriodin III) (average particle (4 .mu.m/3) diameter/mass
parts) BN (SP-2) (average particle (4 .mu.m/5) diameter/mass parts)
SnO.sub.2 (SN-100D) (Sb doped SnO.sub.2) (0.7/10) (average particle
diameter/mass parts) Comparative Comparative Comparative Example 6
Example 7 Example 1 Example 2 Example 3 Structure of a PFA PFA
powder (Low melt (Low melt (Low melt (Low melt (Low melt surface
layer (100 mass parts) (average particle viscosity) viscosity)
viscosity) viscosity) viscosity) composition diameter/mass parts)
(18 .mu.m/40) (18 .mu.m/40) (8 .mu.m/15) (18 .mu.m/40) (18
.mu.m/40) Small particle diameter (High melt (High melt (Low melt
(High melt (High melt PFA (average particle viscosity) viscosity)
viscosity) viscosity) viscosity) diameter/mass parts) (0.2
.mu.m/60) (0.2 .mu.m/60) (0.2 .mu.m/85) (0.2 .mu.m/60) (0.2
.mu.m/60) Filler BaSO.sub.4 (BA) (BA) (BA) (mass parts) (average
particle (8 .mu.m/10) (8 .mu.m/15) (8 .mu.m/33) diameter/mass
parts) Zeolite (average particle (2 .mu.m/5) diameter/mass parts)
Mica (average particle diameter/mass parts) BN (average particle
diameter/mass parts) SnO.sub.2 (Sb doped SnO.sub.2) (average
particle diameter/mass parts)
[0079]
2 TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Comparative
Comparative Comparative ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7
Example 1 Example 2 Example 3 Material Friction coefficient 0.054
0.056 0.051 0.050 0.057 0.057 0.055 0.073 0.066 0.065
characteristics at high temperatures (with J paper) Contact angle
with 115 114 115 115 114 115 112 113 113 110 water (.degree.)
Surface roughness 1.1 0.9 1.0 1.3 0.8 1.6 2.7 0.15 0.2 3.5 (Ra)
(.mu.m) Surface gloss 28 36 39 29 35 35 22 77 75 7 Evaluation of
waviness 0.53 0.58 0.45 0.68 0.65 0.75 0.86 0.25 0.77 1.5
Evaluation Durability to paper .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. x x .smallcircle. wrinkles Image glossiness when
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. x an image is formed on both surfaces OHP image
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .DELTA. .DELTA. .smallcircle. .DELTA. x transmission
unevenness White void of an .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. .DELTA. .DELTA.
.smallcircle. .smallcircle. x image Paper abrasive trace
.smallcircle. .smallcircle. .smallcircle. .smallcircle.
.smallcircle. .smallcircle. .smallcircle. x x .smallcircle.
Example 1
[0080] In the first example, a fluororesin solution (manufactured
by Mitsui.cndot.Du Pont Flurochemical) prepared by mixing a PFA
powder having an average particle diameter of 8 .mu.m and a low
melt viscosity (0.3.times.10.sup.4 to 0.5.times.10.sup.4
Pa.multidot.s; 380.degree. C.) with a PFA dispersion, prepared by
dispersing a PFA fine particle having an average particle diameter
of. 0.2 .mu.m and a low melt viscosity (0.3.times.10.sup.4 to
0.5.times.10.sup.4 Pa.multidot.s; 380.degree. C.) in an aqueous
solvent, in the following ratio: PFA powder/PFA fine
particle=15/85, is used as the material of the surface layer.
[0081] Also, as the filler particle, barium sulfate (BMH-60,
manufactured by Sakai Chemical Industry Co., Ltd.: average particle
diameter: 5 .mu.m, and content of a large particle 15 .mu.m or more
in size is 2 mass % or less) is used and compounded in an amount of
10 mass parts based on 100 mass parts of PFA.
[0082] Here, the ratio of "PFA powder/PFA fine particle=15/85"
means that the PFA powder is about 18 mass parts per 100 mass parts
of the PFA fine particle. This ratio exists not only within the
aforementioned preferable range, namely, "the PFA powder is 5 mass
parts or more and 70 mass parts or less per 100 mass parts of the
PFA fine particle" but also within the aforementioned more
preferable range, namely, "the PFA powder is 5 mass parts or more
and 30 mass parts or less per 100 mass parts of the PFA fine
particle".
[0083] Also, the characteristics of the filler particle that "the
amount of a large particle 15 .mu.m or more in size is 2 mass % or
less" ensures that the ratio of the filler particle exists not only
within the aforementioned preferable range, namely, "particles
having a particle diameter of 15 .mu.m or more is 25 mass % or
less" but also within the aforementioned more preferable range,
namely, "particles having a particle diameter of 15 .mu.m or more
is 5 mass % or less" and within the aforementioned still more
preferable range, namely, "particles having a particle diameter of
15 .mu.m or more is 3 mass % or less".
[0084] The gloss of the surface layer in the first example is 28 as
the value measured by a 75.degree. micro-gloss meter (BYK Gardner).
Also, the surface roughness Ra of the surface layer is 1.1 .mu.m
and the filtered wave center waviness of the surface layer is 0.53
.mu.m in the condition of a cutoff of 0.25 mm. Further, the static
friction coefficient of the surface layer with common paper at
100.degree. C. is measured and as a result, found to be 0.054. In
the measurement, a Friction Player manufactured by RHESCA COMPANY,
LIMITED is used, J paper manufactured by Fuji Xerox Co., Ltd. is
used as the common paper and the rotating speed of the table is 0.5
mm/sec (reciprocating motion (angle of rotation: 10.degree.)).
Example 2
[0085] In the second example, the same material in the first
example is used except that zeolite (Toyobuilder (manufactured by
Tosoh Corporation), average particle diameter: 2 .mu.m) is used as
the filler particle in place of barium sulfate in the first example
in an amount of 5 mass parts in 100 mass parts of PFA.
[0086] Here, the proportion of "5 mass parts" of the filler
particle is close to the lower limit of the aforementioned
preferable proportion, namely, "the amount of the inorganic fine
particle is 3 mass parts or more and 15 mass parts or less based on
100 mass parts of the fluororesin".
[0087] The gloss of the surface layer in the second example is 36
as the value measured by a 75.degree. micro-gloss meter (BYK
Gardner). Also, the surface roughness Ra of the surface layer is
0.9 .mu.m and the filtered wave center waviness of the surface
layer is 0.58 .mu.m in the condition of a cutoff of 0.25 mm.
Further, the static friction coefficient of the surface layer with
a common paper at 100.degree. C. is measured and as a result, found
to be 0.056.
Example 3
[0088] In the third example, the same material in the first example
is used except that as the filler particle, a mixture of barium
sulfate (BMH-60, manufactured by Sakai Chemical Industry Co., Ltd.,
average particle diameter: 5 .mu.m, large particles having a
particle diameter of 15 .mu.m or more is 2 mass % or less) and mica
(Iriodin.sup.(R) 111 manufactured by Japan Merk Co., Ltd.) is used,
and barium sulfate and mica are compounded in an amount of 5 mass
parts and in an amount of 3 mass parts respectively based on 100
mass parts of PFA. Namely, in this example, the mixture of plural
types of filler materials is used.
[0089] The gloss of the surface layer in the third example is 39 as
the value measured by a 75.degree. micro-gloss meter (BYK Gardner).
Also, the surface roughness Ra of the surface layer is 1.0 .mu.m
and the filtered wave center waviness of the surface layer is 0.45
.mu.m in the condition of a cutoff of 0.25 mm. Further, the static
friction coefficient of the surface layer with a common paper at
100.degree. C. is measured and as a result, found to be 0.051.
Example 4
[0090] In the fourth example, the same material in the first
example is used except that boron nitride (SP-2, manufactured by
Denki Kagaku Kogyo Kaisha) is used as the filler particle in place
of barium sulfate used in the first example in an amount of 5 mass
parts in 100 mass parts of PFA.
[0091] Here, the proportion of "5 mass parts" of the filler
particle in this example is close to the lower limit of the
aforementioned preferable proportion, namely, "the amount of the
inorganic fine particle is 3 mass parts or more and 15 mass parts
or less based on 100 mass parts of the fluororesin".
[0092] The gloss of the surface layer in the fourth example is 29
as the value measured by a 75.degree. micro-gloss meter (BYK
Gardner). Also, the surface roughness Ra of the surface layer is
1.3 .mu.m and the filtered wave center waviness of the surface
layer is 0.68 .mu.m in the condition of a cutoff of 0.25 mm.
Further, the static friction coefficient of the surface layer with
a common paper at 100.degree. C. is measured and as a result, found
to be 0.050.
[0093] The filtered wave center waviness "0.68 .mu.m" in this
example is within the aforementioned preferable range "0.9 .mu.m or
less in the condition of a cutoff of 0.25 mm" and is also the very
upper limit within the aforementioned more preferable range "0.7
.mu.m or less".
Example 5
[0094] In the fifth example, the same material in the first example
is used except that a water dispersion (SN-100D, manufactured by
Ishihara Sangyo Kaisha Ltd., average particle diameter: 0.7 .mu.m)
of tin oxide (Sb doped SnO.sub.2) is used as the filler particle in
place of barium sulfate used in the first example in an amount of
10 mass parts based on 100 mass parts of PFA. Here, the average
particle diameter "0.7 .mu.m" of the filler particle in this
example is close to the lower limit of the aforementioned
preferable range, namely, "0.1 .mu.m or more and 15 .mu.m or
less".
[0095] The gloss of the surface layer in the fifth example is 35 as
the value measured by a 75.degree. micro-gloss meter (BYK Gardner).
Also, the surface roughness Ra of the surface layer is 0.8 .mu.m
and the filtered wave center waviness of the surface layer is 0.65
.mu.m in the condition of a cutoff of 0.25 mm. Further, the static
friction coefficient of the surface layer with a common paper at
100.degree. C. is measured and as a result, found to be 0.057.
[0096] This static friction coefficient "0.057" is a coefficient
close to the upper limit of the above defined range reading as
follows "the surface static friction coefficient with common paper
at 100.degree. C. is 0.06 or less".
Example 6
[0097] In the sixth example, a fluororesin solution (710CL,
manufactured by Mitsui.cndot.Du Pont Flurochemical) prepared by
mixing a PFA powder having an average particle diameter of 18 .mu.m
and a low melt viscosity (0.3.times.10.sup.4 to 0.5.times.10.sup.4
Pa.multidot.s; 380.degree. C.) with a PFA dispersion, prepared by
dispersing a PFA fine particle having an average particle diameter
of 0.2 .mu.m and a high melt viscosity (2.7.times.10.sup.4 to
2.9.times.10.sup.4 Pa.multidot.s; 380.degree. C.) in an aqueous
solvent, in the following ratio: PFA powder/PFA fine
particle=40/60, is used as the material of the surface layer.
[0098] Also, as the filler particle, barium sulfate (BA,
manufactured by Sakai Chemical Industry Co., Ltd.: average particle
diameter: 8 .mu.m, and content of a large particle 15 .mu.m or more
in size is 17 mass %) is used and compounded in an amount of 10
mass parts based on 100 mass parts of PFA.
[0099] Here, the average particle diameter "18 .mu.m" of the PFA
powder exists within the aforementioned preferable range reading as
follows "3 .mu.m or more and 30 .mu.m or less", but exceeds the
upper limit of the aforementioned more preferable range reading as
follows "3 .mu.m or more and 15 .mu.m or less".
[0100] The melt viscosity of the PFA fine particle, that is,
"2.7.times.10.sup.4 to 2.9.times.10.sup.4 Pa.multidot.s;
380.degree. C." satisfies the aforementioned definition reading as
follows "3.5.times.10.sup.4 Pa.multidot.s or less at 380.degree.
C.", but is out of the more preferable range defined above, which
reads as follows "the melt viscosity at 380.degree. C. is
1.5.times.10.sup.4 Pa.multidot.s or less".
[0101] Moreover, the ratio "PFA powder/PFA fine particle=40/60"
means that that the proportion of the PFA powder is about 67 mass
parts per 100 mass parts of the PFA fine particle and is close to
the upper limit of the aforementioned preferable range reading as
follows "the amount of the PFA powder is 5 mass parts or more and
70 mass parts or less per 100 mass parts of the PFA fine
particle".
[0102] Also, the characteristics of the filler particle that "the
amount of a large particle 15 .mu.m or more in size is 17 mass %"
ensures that the ratio of the filler particle exists within the
aforementioned preferable range reading as follows "particles
having a particle diameter of 15 .mu.m or more is 25 mass % or
less" but exceeds the aforementioned more preferable range reading
as follows "particles having a particle diameter of 15 .mu.m or
more is 5 mass % or less".
[0103] The gloss of the surface layer in the sixth example is 35 as
the value measured by a 75.degree. micro-gloss meter (BYK Gardner).
Also, the surface roughness Ra of the surface layer is 1.6 .mu.m
and the filtered wave center waviness of the surface layer is 0.75
.mu.m in the condition of a cutoff of 0.25 mm. Further, the static
friction coefficient of the surface layer with a common paper at
100.degree. C. is measured and as a result, found to be 0.057.
[0104] In this sixth example, a filler particle different from the
filler particle used in the fifth example is used. Like the fifth
example, this sixth example has a static friction coefficient of
"0.057" which is close to the defined value, which reads as follows
"the surface static friction coefficient with common paper at
100.degree. C. is 0.06 or less" in the present invention. Also, the
filtered wave center waviness "0.75 .mu.m" in this sixth example is
within the aforementioned preferable range reading as follows "0.9
.mu.m or less in the condition of a cutoff of 0.25 mm" but somewhat
exceeds the upper limit of the aforementioned more preferable range
reading as follows "0.7 .mu.m or less".
Example 7
[0105] In the seventh example, the same material that is used in
Example 6 is used except that the proportion of the filler particle
is changed to 15 mass parts based on 100 mass parts of PFA.
[0106] Here, the proportion of the filler particle, namely, "15
mass parts based on 100 mass parts of PFA" is equal to the upper
limit of the aforementioned preferable proportion reading as
follows "the amount of the inorganic fine particle is 3 mass parts
or more and 15 mass parts or less based on 100 mass parts of the
fluororesin".
[0107] The gloss of the surface layer in the seventh example is 22
as the value measured by a 75.degree. micro-gloss meter (BYK
Gardner). Also, the surface roughness Ra of the surface layer is
2.7 .mu.m and the filtered wave center waviness of the surface
layer is 0.86 .mu.m in the condition of a cutoff of 0.25 mm.
Further, the static friction coefficient of the surface layer with
common paper at 100.degree. C. is measured and as a result, found
to be 0.055. The surface roughness "2.7 .mu.m as Ra" is close to
the limit of the aforementioned preferable range reading as follows
"3 .mu.m or less as Ra".
[0108] Also, the filtered wave center waviness "0.86 .mu.m" in this
example is the very upper limit of the aforementioned preferable
range reading as follows "0.9 .mu.m or less in the condition of a
cutoff of 0.25 mm".
Comparative Example 1
[0109] In the first comparative example, only PFA is used as the
material of the surface layer and as the PFA, the same PFA that is
used in Example 1 is used.
[0110] The gloss of the surface layer in the first comparative
example is 77 as the value measured by a 75.degree. micro-gloss
meter (BYK Gardner). Also, the surface roughness Ra of the surface
layer is 0.15 .mu.m and the filtered wave center waviness of the
surface layer is 0.25 .mu.m in the condition of a cutoff of 0.25
mm. Further, the static friction coefficient of the surface layer
with common paper at 100.degree. C. is measured and as a result,
found to be 0.073.
[0111] The value "77" of the surface gloss measured here exceeds
the upper limit of the aforementioned preferable range reading as
follows "15 or more and 60 or less" and the static friction
coefficient "0.073" exceeds the limit of the defined value reading
as follows "the static friction coefficient with common paper at
100.degree. C. is 0.06 or less" in the present invention.
Comparative Example 2
[0112] In the second comparative example, only PFA is used as the
material of the surface layer in the same way as in the first
comparative example and as the PFA, the same PFA that is used in
the sixth and seventh examples is used.
[0113] The gloss of the surface layer in the second comparative
example is 75 as the value measured by a 75.degree. micro-gloss
meter (BYK Gardner). Also, the surface roughness Ra of the surface
layer is 0.2 .mu.m and the filtered wave center waviness of the
surface layer is 0.77 .mu.m in the condition of a cutoff of 0.25
mm. Further, the static friction coefficient of the surface layer
with a common paper at 100.degree. C. is measured and as a result,
found to be 0.066.
[0114] The value "75" of the surface gloss measured here exceeds
the upper limit of the aforementioned preferable range reading as
follows "15 or more and 60 or less" and the static friction
coefficient "0.066" somewhat exceeds the limit of the defined value
reading as follows "the static friction coefficient with common
paper at 100.degree. C. is 0.06 or less" in the present invention.
Also, the filtered wave center waviness "0.77 .mu.m" is within the
aforementioned preferable range reading as follows "0.9 .mu.m or
less in the condition of a cutoff of 0.25 mm" but exceeds the
aforementioned more preferable range reading as follows "0.7 .mu.m
or less" to some extent.
Comparative Example 3
[0115] In the third comparative example, the same material that is
used in the sixth or seventh example is used except that the
proportion of the filler particle is changed to 33 mass parts based
on 100 mass parts of PFA.
[0116] Here, the proportion of the filler particle which reads as
follows "33 mass parts based on 100 mass parts of PFA" somewhat
exceeds the upper limit of the aforementioned range reading as
follows "the content of the inorganic fine particle is 1 mass part
or more and 30 mass parts or less based on 100 mass parts of the
fluororesin".
[0117] The gloss of the surface layer in the third comparative
example is 7 as the value measured by a 75.degree. micro-gloss
meter (BYK Gardner). Also, the surface roughness Ra of the surface
layer is 3.5 .mu.m and the filtered wave center waviness of the
surface layer is 1.5 .mu.m in the condition of a cutoff of 0.25 mm.
Further, the static friction coefficient of the surface layer with
common paper at 100.degree. C. is measured and as a result, found
to be 0.065.
[0118] The value "7" of the surface gloss measured here is less
than the lower limit of the aforementioned preferable range reading
as follows "15 or more and 60 or less", the filtered wave center
waviness "1.5 .mu.m" exceeds the upper limit of the aforementioned
preferable range reading as follows "0.9 .mu.m or less in the
condition of a cutoff of 0.25 mm" and the surface roughness "3.5
.mu.m as Ra" exceeds the limit of the aforementioned preferable
range reading as follows "3 .mu.m or less as Ra".
[0119] (Result of Evaluation)
[0120] The results of evaluation as to each of the examples and
comparative examples as described above will be explained
hereinbelow.
[0121] Each of the aforementioned examples and comparative examples
is mounted on DocuCenter Color 400 color composite machine to run
50000 sheets of normal P paper manufactured by Fuji Xerox Co., Ltd.
Then, 100 sheets of P paper are run with making a halftone image
having an image density of 50%. At this time, evaluations are made
as to the occurrence of paper wrinkles, image glossiness and image
white void when an image is formed on both surfaces and the
generation of abrasive traces at the end part of a paper. Also,
image transmission unevenness when forming an image by using OHPs
(OHP V516, manufactured by Fuji Xerox Co., Ltd.) is also
evaluated.
[0122] In all the first to fifth examples, paper wrinkles, image
white voids, abrasive traces and transmission unevenness are not
caused and image glossiness is also good.
[0123] Also, in the sixth and seventh examples, no paper wrinkle
occurred and the image transmission unevenness in OHP printing is
practically no-problem level though the transmission unevenness is
observed a little. Also, the image void when forming an image on
both surfaces is practically no-problem level though it is
partially observed, abrasive traces at the end of a common paper
are not caused and image glossiness when forming an image on both
surfaces is good.
[0124] Accordingly, it is confirmed that each of the first to
seventh examples is free from any practical problem and has good
characteristics.
[0125] On the other hand, in the first comparative example, the
generation rate of paper wrinkles is 50%, abrasive traces at the
end of a paper occurred. When running a larger size paper to form
an image, abrasive traces emerged as image defects. The image
transmission unevenness in OHP printing and the image void when
forming an image on both surfaces are not caused and the image
glossiness when forming an image on both surfaces is good.
[0126] Also, in the second comparative example, the generation rate
of paper wrinkles is 30%, abrasive traces at the end of a paper
occurred. When running a larger size paper to form an image,
abrasive traces emerged as image defects. The image transmission
unevenness in OHP printing is observed a little but this is
practically no-problem level, there is no image void when forming
an image on both surfaces, and the image glossiness when forming an
image on both surfaces is good.
[0127] Further, in the third comparative example, image
transmission unevenness in OHP printing is significantly observed
though paper wrinkles and abrasive traces at the end of a paper are
unobserved. Also, image glossiness when forming an image on both
surfaces is insufficient and there is a significant difference in
gloss between the front side and backside images. Further, image
voids when forming an image on both surfaces are observed in the
condition of an image density of about 50%.
[0128] These image defects are all image defects on a level which
could not stand to practical use.
[0129] The above results of evaluation will be analyzed
hereinbelow.
[0130] First, when comparing the results of evaluation in each
example with the results of evaluation in each comparative example,
almost the same good results of evaluation are obtained though the
static friction coefficients with common paper at 100.degree. C.
extended over a range from 0.050 to 0.057 in seven examples,
whereas the static friction coefficient extended over a range from
0.065 to 0.073 in three comparative examples and it is found that
all of these comparative examples exhibit serious disorders. This
result permits to estimate the existence of a point where the
rating is changed largely among static friction coefficients
ranging from "0.057" to "0.065". This value of the static friction
coefficient is expected to be larger than 0.060 at least from the
trend in the above each example and comparative example. Therefore,
if "the static friction coefficient with common paper at
100.degree. C. is 0.060 or less", the object of the present
invention can be attained.
[0131] It is also understood that the rating is greatly dropped if
the surface gloss is deviated from any of the upper limit and lower
limit of the aforementioned defined range reading as follows "15 or
more and 60 or less as the value measured by a 75.degree.
micro-gloss meter (BYK Gardner)". Because it is difficult to obtain
examples in which only the surface gloss is changed, there is no
data showing the very upper and lower limits of gloss. However, the
lower limit "15" indicates a transition point that is inferred from
the correlation between the desirable gloss of an image and the
surface gloss of the surface layer and the upper limit "60"
indicates a transition point that is inferred from the correlation
between the surface gloss of the surface layer and the generation
of paper wrinkles. The results of evaluation shows that the above
examples and comparative examples are typical examples supporting
these inferences.
[0132] When comparing the measured value of the filtered center
waviness with the image transmission unevenness in OHP printing in
each example and comparative example, it has been confirmed that no
transmission unevenness is caused if the waviness is 0.7 .mu.m or
less, there is no practical problem though transmission unevenness
is partially observed if the waviness exceeds 0.7 .mu.m and
practically unfavorable transmission unevenness is caused if the
waviness exceeds 0.9 .mu.m. As a consequence, the foregoing
definition of a preferable range which reads as follows "0.9 .mu.m
or less in the condition of a cutoff of 0.25 mm" and the foregoing
definition of a more preferable range which reads as follows "0.7
.mu.m or less in the condition of a cutoff of 0.25 mm" are both
appropriate.
[0133] It has been also confirmed from the results of evaluation of
each of the sixth and seventh examples that good results of
evaluation are obtained to the very upper limit of the foregoing
defined range reading as follows "the content of the PFA powder is
5 mass parts or more and 70 mass parts or less based on 100 mass
parts of the PFA fine particle" in relation to the ratio of the PFA
powder to PFA fine particle to be compounded.
[0134] Comparison between the results of evaluation of the seventh
example with the results of evaluation of the third comparative
example shows that the upper limit of the foregoing definition "3
.mu.m or less as Ra" as to the surface roughness of the surface
layer is reasonable.
[0135] Also, comparison between the results of evaluation of each
of the first to fifth examples and the results of evaluation of
each of the sixth and seventh examples shows that the deviation
from all of the aforementioned more preferable range reading as
follows "3 .mu.m or more and 15 .mu.m or less) as to the average
particle diameter of the PFA powder, the aforementioned more
preferable range reading as follows "the melt viscosity at
380.degree. C. is 1.5.times.10.sup.4 Pa.multidot.s or less" as to
the melt viscosity of the PFA fine particle, the aforementioned
more preferable range reading as follows "the content of the PFA
powder is 5 mass parts or more and 30 mass parts or less based on
100 mass parts of the PFA fine particle" as to the ratio of the PFA
fine particle to the PFA powder and the aforementioned more
preferable range reading as follows "the content of particles
having a particle diameter of 15 .mu.m or more is 5 mass % or less"
as to the filler particle, causes transmission unevenness of an OHP
image and voids of both-surface image though each example is on a
practically no-problem level. Accordingly, it is predicted that
products having a surface layer satisfying the requirement as to
one or more of these more preferable ranges will stand comparison
with the first to fifth examples.
[0136] It is understood that the provision of a surface layer
having surface characteristics fulfilling the requirement as to the
aforementioned ranges makes it possible to obtain a highly reliable
circulating body.
* * * * *